Parts and Shapes of Active Volcanoes - Report Example

Active Volcanoes Name: Institution: Active Volcanoes The geological and geographical understanding of volcanoes is comprised of both theoretical and proven claims. This is because of the existences of evident volcanic activities and the availability of theoretical explanations to why they form of how they are formed. The simplest definition of a volcano can be a rupture or opening in or on the earth’s surface or any planetary object, that allows hot volcanic ash, lava or gases, from the magma chamber to escape below or above the earth’s surface (Siebert, Simkin & Kimberly, 2010). Geologically, volcanic activities are visible in places with diverging or converging tectonic plates. Therefore, it is essential that this report focuses on looking at what active volcanoes are in terms of shapes and parts and practically give accounts of where in the world they are situated. In addition, the report looks into the causes of a volcanic eruption and the materials that such eruptions produce. Finally it looks at the famous volcanic eruptions and where they occurred and their impacts on the places where they occurred. Parts and shapes or an active volcano Parts of an active volcano Fig1, Source: http://resources.woodlands-junior.kent.sch.uk/Homework/mountains/volcanoparts.html Figure 1 above shows a cross-sectional view of various parts of an active volcano. In order to understand more about the diagram, it is essential to mention each part in the figure with proper explanations. First, the magma reservoir refers to the reservoir of the molten rock material found beneath the surface of the earth (Saunders, et al, 2013). This material forces itself out of the vent and comes out as lava. In the event of a volcanic eruption, there are some small cone-shaped volcanoes that are always formed through the process of volcanic debris accumulation; such accumulations always lead to the formation of the parasitic cone. This is formed when the magma reaches the surface (Barroe, 2009). However, in some circumstances, the magma fails to reach the surface of the earth’s crust and accumulates in the crack inside the volcano. In such cases a sill is formed, which is a flat rock piece resulting from hardening of magma in the cracks of a volcano. Moreover, the processes of having magma reach in or one the earth’s surface from the magma reservoir requires a passage, which is composed of a weaker material easily melted by hot magma. This passage refers to as the vent, which is an opening allowing volcanic material to escape on the earth’s surface (Barroe, 2009). As magma shoots out through the vents, there are molten rocks that erupt, solidify and cool as the eruption continues. This molten rock is called lava as is evident from the figure above (Poland, Hamburger & Newman, 2006). In the event that an eruption stops, and the magma in the vent or conduit stops erupting, it cools down and recedes a little bit, causing a crater at the top of the volcano, or on any vent that reached the top surface. Such craters can form crater lakes in the event they are accumulated with water. Conduits on the other hand refer to the underground passage that is used by magma to travel through (Barroe, 2009). On the other hand, Ash and Ash clouds refer to the blasting fragments of rock or lava during a volcanic eruption and their clouds formed as the eruption occurs respectively. Shapes of an active volcano Any active volcano can take one of the four common shapes of any volcano. They can be flat, forming shield volcanoes in areas where magma runs for a long time allowing the gas to escape easily without explosions. This forms a shield or bowl like shape in the middle and lava flows forming the long gentle slopes. On the other hand, active volcanoes can take the tall and thin shapes forming composite volcanoes (Lockwood & Hazlett, 2010). This forms when magma is thick and sticky and the gas does not escape resulting to a built up and an explosion. They are steep-sided and have many volcanic rock layers made of rock debris, ash and sticky lava. There are also cinder cone shaped volcanoes in which oval or circular cones are built up from eruptions of lava breaking into smaller pieces and shoots into the air (Moitra, et al, 2013). The falling back of the small pieces to the group, cooling and forming cinders around the vents leads to the formation of a volcano of this shape. Finally, lava domes forms the last shape of a volcano in which erupting lava forms domes because of the flow of thick lava, which results to steep-sided mound due to the piling up of lava close to the volcanic vent. According to Leontiou (2010), the most active volcanoes in the world happen in the Pacific Ring of Fire with an average of 50-70 volcanic eruptions each year. These include the Mt. Yasur Vanautu, which has erupted in 111 years on the Tanna Island; Mt. Etna in Italy had its eruption going for 109 years on the Island of Sicily, Stromboli, Italy for 108 years, and Mt. Santa Maria in Guatemala erupting for 101 years, located in the Guatemala’s Pacific Coastal Plain. There is also Mt. Sangay, in Eduador, which has erupted in 94 years. Causes and materials of volcanic eruptions A volcanic eruption occurs when the upper mantle melts forming magma. According Kilinc (2008), volcanoes refer to the vents or openings through which the magma flows. The pressure of the absolved gases and the buoyancy of magma alongside an inject of magma into the chambers already filled with magma results to an eruptive process as the rock inside the earth's crust melts. This melting process results in an imbalance between the mass, which remains the same while having its volume increasing. This leads to a production of a reduced in dense magma than that of the surrounding rock (Sakellariou, et al, 2012). Due to these changes, the hot magma rises due to buoyancy towards the surface. In the process of this eruption, rhyolitic and andesitic compositions have volatile materials dissolved in them such as sulphur IV Oxide, water and Carbon IV Oxide. In addition, the injection of fresh magma into an already cooled vent or conduit also results to a volcanic eruption. This is because magma is forced to move up and due to built in pressure, explodes. This explains why several eruptions result in the production of huge quantities of dust and gases (Lanzafame, at al, 2013). The continuous enormous rise of magma under pressure into the cracks of the earth’s crust can also lead to the formation of crack whenever they are not available. On reaching the surface, the magma is called lava. In addition, the tectonic plate movements also lead to formation of volcanic eruptions. The tectonic plates in the earth’s crust lie above the molten and hot mantle. Since every plate has a continent crust with oceanic crust above them, the presence of huge magma currents deep in the mantle also causes these plates to move, in a very slow pace on the earth’s crust. This slow movement is also believed to expose the molten magma, which passes through the vents of the crust. An evident explanation of this is in the fact that most of the world’s largest volcanic eruptions occur along the plate boundary edges such as the Pacific Ring of Fire, which contains some of the most active volcanoes. A volcanic eruption produces lava, which is a composition of various chemicals and materials. An erupting magma typically contains a very high percentage of silica, in most circumstances referred to as Felsic lava by most geologists. The felsic lava has very high viscosity (Shea, et al, 2010). This material is composed of silicon, magnesium, aluminium, oxygen, calcium, iron, potassium, sodium, titanium, carbon, hydrogen, phosphorus, and sulphur. These are the most common material elements found in an erupted volcano. However, in order to aid in understanding, most geologists group volcanic materials into two main groups, as lava flow materials or as pyroclastic materials (Scrope, 2011). The lava flow materials are composed of Aa, which is a rough, spiny, and jagged lava with a clinker surface. There are also the blocks, lava, lava flow, pahoehoe and pillow lava. On the other hand, pyroclastic materials include the agglutinate, ash, blocks, cinders, lapilli, pumice, reticulate, scoria and tephra. Famous volcanic eruptions and their impacts Historical aspects of volcanic eruptions reveal that there are several famous volcanic eruptions that cannot go unnoticed. One of such famous volcanic eruptions of all times is in Thera, Greece in 1600 BC. This occurred because of the collapse of the Ninoan civilization. Archaeologists believe that this is a representation of a volcanic eruption since the two towns were destroyed leading to the decline of their civilization (Heiken, 2013). However, this notion or theoretical explanation is fiction though scientists and geologists have never disputed it. However, the beginning of the eruption of Mount Vesuvius in Italy in AD 79 marks one of the most deadly volcanic eruptions of time (Darley, 2011). This volcanic eruption wiped out an entire composite of Roman Cities of Pompeii and Herculaneum. The most rational explanation given to the high presence of volcanic eruptions in Italy has been the movement of the plate tectonics. With a column of pumice going up to 15 miles, and the presence of strong wind, the eruption of Vesuvius resulted in a glowing avalanche at the speed of 62 miles per hour. However, over the last 5,000 years, the Hatepe volcanic eruption in New Zealand is considered the largest. History indicates that the eruption reached 31 miles in height with a pyroclastic flow covering over 50 miles away. This eruption marks Lake Taupo’s last major eruption of the time. In 1669, a volcanic eruption occurred in Italy forming the Mount Etna. With an earthquake and consequent flow of lava signalling the beginning of the volcanic eruption, it destroyed over 40 towns and left close to 60,000 people homeless. There is also the Tambora Volcanic Eruption in Indonesia in 1815, which released millions of tons of Sulphur IV Oxide (Kasatkina et al 2013). This eruption is believed to have led to an immediate cooling of the earth’s surface, which lead to the 1816’s “year without summer” in America and Europe. There was also the Krakatoa eruption in Indonesia, which resulted in having shock waves and noise experienced in the whole world in 1883 (Sakellariou, et al, 2012). This eruption caused the temperature of the earth’s surface to feel just like the Tambora eruption, with the largest ever recorded natural explosion in history. In conclusion, it is evident that volcanic activities have been and will continue to be one of the most unexpected natural disasters. The process and activities that lead to the formation of a volcanic eruption is unpredictable since the accuracy of prediction cannot be measured with precision. This has led to the occurrence of the most deadly eruptions of the time, as is evident in the a few mentioned examples. It is also evident that while these eruptions offer unpredictable events, studying them have become one of the most interesting aspects of geologists and geographers. References: Kilinc, A. (2008). ‘What Causes a Volcano to erupt and how do scientists predict eruptions?’ accessed October 1, 2013 from http://www.scientificamerican.com/article.cfm?id=what-causes-a-volcano-to Leontiou, A. (2010). ‘The World’s five most active volcanoes’ accessed October 1, 2013 from http://www.livescience.com/29790-worlds-five-most-active-volcanoes.html Barroe, M. (2009). ‘Types of Volcanoes and the Shapes of Volcanoes’ accessed October 1, 2013 from http://resources.woodlands-junior.kent.sch.uk/Homework/mountains/volcanotypes.html Siebert, L., Simkin, T., & Kimberly, P. (2010). Volcanoes of the World. California: University of California Press. Sakellariou, D., Rousakis, G., Nomikou, P., Bell, K. C., Carey, S., & Sigurdsson, H. (2012, June). Tsunami Triggering Mechanisms Associated with the 17 th cent. BC Minoan Eruption of Thera Volcano, Greece. In The 22nd International Offshore and Polar Engineering Conference, Tsunami and Safety Symposium, Rhodes, Greece. Kasatkina, E. A., Shumilov, O. I., Timonen, M., & Kanatjev, A. G. (2013). Consequences of powerful volcanic eruptions according to dendrochronological data. Izvestiya, Atmospheric and Oceanic Physics, 49 (4), 432-438. Lockwood, J. P., & Hazlett, R. W. (2010). Volcanoes: global perspectives. Hoboken: John Wiley & Sons. Darley, G. (2011). Vesuvius: the most famous volcano in the world. New York: Profile Books. Heiken, G. (2013). Dangerous neighbor: Volcanoes and Cities. Cambridge: Cambridge University Press. Saunders, K., Blundy, J., Dohmen, R., & Cashman, K. (2012). Linking petrology and seismology at an active volcano. Science, 336 (6084), 1023-1027. Moitra, P., Gonnermann, H. M., Houghton, B. F., & Giachetti, T. (2013). Relating vesicle shapes in pyroclasts to eruption styles. Bulletin of Volcanology, 75 (2), 1-14. Poland, M., Hamburger, M., & Newman, A. (2006). The changing shapes of active volcanoes: History, evolution, and future challenges for volcano geodesy. Journal of Volcanology and geothermal research, 150 (1), 1-13. Lanzafame, G., Mollo, S., Iezzi, G., Ferlito, C., & Ventura, G. (2013). Unraveling the solidification path of a pahoehoe “cicirara” lava from Mount Etna volcano. Bulletin of Volcanology, 75 (4), 1-16. Shea, T., Houghton, B. F., Gurioli, L., Cashman, K. V., Hammer, J. E., & Hobden, B. J. (2010). Textural studies of vesicles in volcanic rocks: an integrated methodology. Journal of Volcanology and Geothermal Research, 190 (3), 271-289. Scrope, G. P. (2011). Volcanos: The Character of Their Phenomena, Their Share in the Structure and Composition of the Surface of the Globe, and Their Relation to Its Internal Forces. Cambridge: Cambridge University Press. Read More